Electrical power distribution systems are useful for providing flexible power delivery options in a broad range of operating environments, including offices, warehouses, garages, and factories to provide an electrical power source for lighting and other electrical devices and equipment. In particular, busway distribution systems must be developed to accommodate structural features and clearance requirements imposed by the workspaces and equipment, raceways, piping, and encumbrances present in the environments for which they are most useful. For example, busbar busway power distribution systems are widely used for powering computer systems in large data centers, and they continue to gain popularity for their growing omnipresence, ease of installation, and ease of custom configuration and re-configuration.
Busway systems include one or more tracks or sections that each contains electrically isolated conductive bars called busbars that extend along an inner length of a track housing of a busway frame and enclosure commonly known as “open channel busway.” The housing may be constructed of extruded aluminum, for example, and provide a ground that meets applicable standards, and may have a withstand rating of at least 22 kA, for example. Preferably, busbar busway power distribution systems are capable of operating continuously without mechanical or electrical damage, degradation, or derating of operating capability under the following example conditions: 1) ambient temperature of electronic components in range from 32 degrees to 104 degrees Fahrenheit (0 degrees to 40 degrees Celsius); 2) relative humidity of 0 percent to 90 percent, non-condensing; and 3) altitude in a range from sea level to 4000 feet (1220 m). Preferably busways should meet UL857, be configured to supply rated full-load current; should be rated to 600 VAC and 600 VDC; and should be fully rated to interrupt symmetrical short-circuit current with a minimum three-cycle short-circuit rating of up to 42 Ka RMS symmetrical. The housing defines an opening or channel that enables access to the busbar contained within the housing. Open channel busway tracks or sections may be joined together to form power distribution circuits.
Busway housing section lengths may be custom defined for a particular application. Busway systems have been developed for side and overhead installation of track sections to a wall or ceiling, respectively, to accommodate a variety or installation options and application limitations imposed by equipment or installation environments. A top of a busway track or section may include or define a slot or channel running along a length of the busway to provide attachment points for installation of the busway in an operating environment. An opposing side or bottom of the busway track may include or define a conductor access opening, which may be a continuous or substantially continuous opening extending along a length of the track or section. The conductor access opening is configured to accept one or more plug-in units and facilitate an electrical connection between a conductive portion of the one or more take-off devices or plug-in units and the conductive busbars disposed in the busway housing.
Busway sections may be connected to one another to form a custom configuration as desired, and may be efficiently re-configured if necessary. Systems may include an end cap installed at an end of a length of busway section(s). A joint kit or bus connector is used to form electrical and mechanical connections between busway sections and power feeds by way of compression or bolted means. A power feed that provides connection from incoming cables to the busway system. The power feed includes an NEMA enclosure having access panels configured for cabling and cable access. The power feed includes an internal connection to a section of busway conductors within a busway. The power feed maybe available as an End Feed or a Center or Top Feed box for accommodating existing wire and conduit feeder runs for termination to the End Feed box.
Busway systems may include conductive busbars formed of pure copper, or copper and aluminum, and may be sized to handle 100% of the busway rating under continuous operation up to the maximum ambient temperature. The conductors should be isolated from the housing. An isolated ground may be implemented in the busway track housing the busbars. The busbars or conductors may include a neutral of 1.732 times the conductor rating, for example. Busbars may be formed of high strength 98% conductivity copper, for example, and should be capable of carrying rated current continuously without exceeding a temperature increase of 55 degrees Celsius based on a 40 degree Celsius ambient temperature.
A take-off device may be inserted into the open channel busway conductor access channel to form an electrical connection with busbars contained therein to enable the take-off device to draw power from the busway. The power may be used to load a range of devices ranging from lighting to larger electronic equipment. Larger ampere ratings of larger take-off devices benefit from enhanced contact area and pressure of a connection between busbars and conductive portions of the take-off devices. Some busway systems are configured to include a busbar assembly having an outer portion that is insulative, and an inner, concentrically nested conductive portion. An outer portion of the busbar assembly provides structural support, while the inner conductive portion is flexible and has spring-like resiliency. The outer portion, which may be formed of aluminum or an alloy, for example, may have a generally U-shape or V-shape, and may include a slot opening through which conductive portions or stabs or a take-off device pass before engaging in pressure contact with the inner conductive portion. In particular, the inner conductive portion may include substantially parallel conductors that together define a conductor channel for accepting and securing by spring-contact the stab within the busbar assembly, and thereby, clamping the stab within the housing of the busway track or section, applying pressure and achieving maximum surface contact between the stab and the conductors. In some systems, the conductive portions may include a substantially planar surface that may not be configured to contact multiple faces of a stab.
Plug-in units or take-off devices or units also interchangeably referred to herein throughout as power heads, mast heads, power delivery outlets, or output boxes, may use a circuit breaker or a fuse for branch circuit protection. Plug-in units are configured to include conductive stabs, as discussed above, for insertion into a slot or channel defined by a track of a busway bar system wherein the inserted stab contacts a conductor or conductive busbars disposed within the track. Plug-in units may have locking clips, bolt-on tabs, or other fastening devices or systems for securing the units to the busway. Plug-in units may include drop cords with cord grips and appropriately configured receptacles. The units may be selected, configured, and arranged for balancing a load based on a quantity of plug-in units and unit types. Plug-in units preferably may have at least 35 amperes of distribution capacity for 250, 400, and 800 ampere systems. Thermal magnetic trip-type circuit breakers for branch circuit protection may be used. The units maybe configured for removal from a busway system without requiring that power delivered to the busway be suspended or shut down, and they may include integrated shutters.